Injection molding machine and control method thereof

Abstract

When controlling each operational process in a molding cycle by variably controlling the number of revolutions of a drive motor 3 in a hydraulic pump 2, a hydraulic pump 2 where at least multiple fixed discharge flow rate Qo and Qs can be set is used as the hydraulic pump 2 . At the same time, the fixed discharge flow rates Qo . . . are set corresponding to operational processes based upon predetermined conditions in advance, respectively, and the hydraulic pump 2 is switched to the fixed discharge flow rates Qo . . . by corresponding to each operational process at the time of molding. At the same time, each operational process is controlled by variably controlling the number of revolutions of the drive motor 3.

1. An injection molding machine, comprising:
 an injection unit, the injection unit having a moving cylinder and an ejecting cylinder; 
 a molding clamp, the molding clamp having an injecting cylinder and a molding clamp cylinder; 
 a hydraulic pump having a plurality of fixed discharge flow rates, including a first fixed discharge flow rate and a second fixed discharge flow rate which is different than the first fixed discharge flow rate; 
 a switching device receiving fluid from the hydraulic pump, the switching device connected to the moving cylinder, the ejecting cylinder, the injecting cylinder and the molding clamp cylinder; and 
 a controller configured to control the hydraulic pump to operate at only one of the fixed discharge flow rates, wherein the controller is further configured to control the hydraulic pump to switch from the first fixed discharge flow rate to the second fixed discharge flow rate, to be corresponding to a change from one operational process of the injection unit to another operational process and configured to control each operational process by variably controlling the number of revolutions of a drive motor in the hydraulic pump wherein the hydraulic pump is a variable discharge type hydraulic pump having a swash plate, and the fixed discharge flow rates are set according to a change into an inclination angle of the swash plate. 
 
     
     
       2. The injection molding machine according to  claim 1 , further comprising a servomotor connected to the swash plate. 
     
     
       3. The injection molding machine according to  claim 1 , wherein the discharge flow rate is set according to the operational processes of the injection unit and molding clamp, the operational processes including a filling process and a pressure maintenance process. 
     
     
       4. The injection molding machine according to  claim 1 , wherein the swash plate angle is small for a slow filling process or a long pressure holding process. 
     
     
       5. The injection molding machine according to  claim 1 , wherein the swash plate angle is large for a fast filling process or a short pressure holding process. 
     
     
       6. The injection molding machine according to  claim 1 , wherein the change from one operational process of the injection unit to another operational process comprises the change in supplying hydraulic fluid to one of the cylinders to supplying hydraulic fluid to another one of the cylinders.